We are developing a novel kind of instrument for the non-invasive study of functional brain activity. This instrument will use near infrared light to localize an activated brain area within a few millimeters and to reconstruct a functional map of the brain. The method is based on frequency-domain techniques: light at two near infrared wavelengths, intensity modulated at 110 MHz, is carried to the measuring probe by fiber optic cables. As several sources (fiber optics) are present on the probe at different distances from each detector, the instrument will provide a 3D localization of the area where the brain activity occurs. During Phase I of this project, a prototype will be assembled modifying two Frequency Domain Tissue Spectrometers developed by ISS; two optical probes will be fabricated as well as the circuitry for control of 32 light sources. The 3D capability of the instrument will be tested at the end of Phase I on preliminary tests acquired on human volunteers. During the Phase II part of the project, the instrument for functional brain imaging will be developed. At the end of Phase II we plan to conduct comparative tests with functional Magnetic Resonance Imaging techniques. PROPOSED COMMERCIAL APPLICATIONS: 1. Optical imaging of brain activity 2. Localization of stimulated brain cellular aggregates